用 raect 写一个 等离子特效背景。

image.png

import * as React from 'react';

export default class LoginBgCanvas extends React.Component {
  componentDidMount() {
    this.drawCanvas();
  }
  public drawCanvas = () => {
    // tslint:disable-next-line: one-variable-per-declaration
    let canvas = document.querySelector('canvas')!,
      ctx = canvas.getContext('2d')!;
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;
    ctx.lineWidth = 0.3;
    ctx.strokeStyle = new Color(150).style;
    let dotsNomber = 400;
    if (canvas.width < 1400) {
      dotsNomber = 200;
    }

    let mousePosition = {
      x: (30 * canvas.width) / 100,
      y: (30 * canvas.height) / 100
    };

    let dots = {
      nb: dotsNomber,
      distance: 100,
      d_radius: 150,
      array: []
    };
    function colorValue(min) {
      return Math.floor(Math.random() * 255 + min);
    }

    function createColorStyle(r, g, b) {
      return 'rgba(' + r + ',' + g + ',' + b + ', 0.8)';
    }

    function mixComponents(comp1, weight1, comp2, weight2) {
      return (comp1 * weight1 + comp2 * weight2) / (weight1 + weight2);
    }

    function averageColorStyles(dot1, dot2) {
      // tslint:disable-next-line: one-variable-per-declaration
      let color1 = dot1.color,
        color2 = dot2.color;

      // tslint:disable-next-line: one-variable-per-declaration
      let r = mixComponents(color1.r, dot1.radius, color2.r, dot2.radius),
        g = mixComponents(color1.g, dot1.radius, color2.g, dot2.radius),
        b = mixComponents(color1.b, dot1.radius, color2.b, dot2.radius);
      return createColorStyle(Math.floor(r), Math.floor(g), Math.floor(b));
    }
    function Color(min) {
      min = min || 0;
      this.r = colorValue(min);
      this.g = colorValue(min);
      this.b = colorValue(min);
      this.style = createColorStyle(this.r, this.g, this.b);
    }

    function Dot() {
      this.x = Math.random() * canvas.width;
      this.y = Math.random() * canvas.height;

      this.vx = -0.5 + Math.random();
      this.vy = -0.5 + Math.random();

      this.radius = Math.random() * 2;

      this.color = new Color();
    }
    Dot.prototype = {
      // tslint:disable-next-line: object-literal-shorthand
      draw: function() {
        ctx.beginPath();
        ctx.fillStyle = this.color.style;
        ctx.arc(this.x, this.y, this.radius, 0, Math.PI * 2, false);
        ctx.fill();
      }
    };

    function createDots() {
      for (let i = 0; i < dots.nb; i++) {
        dots.array.push(new Dot());
      }
    }

    function moveDots() {
      for (let i = 0; i < dots.nb; i++) {
        let dot = dots.array[i];

        if (dot.y < 0 || dot.y > canvas.height) {
          dot.vx = dot.vx;
          dot.vy = -dot.vy;
        } else if (dot.x < 0 || dot.x > canvas.width) {
          dot.vx = -dot.vx;
          dot.vy = dot.vy;
        }
        dot.x += dot.vx;
        dot.y += dot.vy;
      }
    }
    function connectDots() {
      for (let i = 0; i < dots.nb; i++) {
        for (let j = 0; j < dots.nb; j++) {
          let i_dot = dots.array[i];
          let j_dot = dots.array[j];

          if (
            i_dot.x - j_dot.x < dots.distance &&
            i_dot.y - j_dot.y < dots.distance &&
            i_dot.x - j_dot.x > -dots.distance &&
            i_dot.y - j_dot.y > -dots.distance
          ) {
            if (
              i_dot.x - mousePosition.x < dots.d_radius &&
              i_dot.y - mousePosition.y < dots.d_radius &&
              i_dot.x - mousePosition.x > -dots.d_radius &&
              i_dot.y - mousePosition.y > -dots.d_radius
            ) {
              ctx.beginPath();
              ctx.strokeStyle = averageColorStyles(i_dot, j_dot);
              ctx.moveTo(i_dot.x, i_dot.y);
              ctx.lineTo(j_dot.x, j_dot.y);
              ctx.stroke();
              ctx.closePath();
            }
          }
        }
      }
    }
    function drawDots() {
      for (let i = 0; i < dots.nb; i++) {
        let dot = dots.array[i];
        dot.draw();
      }
    }

    function animateDots() {
      ctx.clearRect(0, 0, canvas.width, canvas.height);
      moveDots();
      connectDots();
      drawDots();

      requestAnimationFrame(animateDots);
    }

    document
      .querySelector('canvas')!
      .addEventListener('mousemove', function(e) {
        mousePosition.x = e.pageX;
        mousePosition.y = e.pageY;
      });

    document
      .querySelector('canvas')!
      .addEventListener('mouseleave', function(e) {
        mousePosition.x = canvas.width / 3;
        mousePosition.y = canvas.height / 3;
      });

    createDots();
    requestAnimationFrame(animateDots);
  };
  render() {
    return ;
  }
}